Electron beam convergence apparatus



Dec. 17, 1963 J. c. scHoPP ELECTRON BEAM CONVERGENCE APPARATUS 3 Sheets-Sheet 1 Filed Aug. 24, 1960 INVENTOR.

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mk @w kw. .SS @SQ Saw n N xm Y mw MME H A\N Nw SSN NNY/fac Q Dec. 17, 1963 J, c. scHoPP' ELEcTRoN BEAM coNvERGENcE APPARATUS 3 Sheets-Sheet 3 Filed Aug. 24. 1960 A ,E Aj A INVEN TOR. Z4/w55 C ffy/@PP e Y dc 3,ll4,358 Patented Dec. 17, i963 3,1%,358 ELECTRGN BEAM C@ WERGENCE APPARATUS James C. Schopp, Merchantvilie, NJ., assigner' to Radio Corporation of America, a corporation of Delaware Filed Aug. 24, 1966, Ser. No. 51,581 Claims. (Cl. 315-22) This invention relates to color television receivers, and particularly to means for making the three electron beams of a color kinescope converge at all scanned points on the kinescope screen.

Color kinescopes of the shadow mask type normally include three electron guns positioned in the neck of the kinescope and a target electrode including an apertured shadow mask between the electron guns and a luminescent screen of phosphor dots arranged in groups of three in registry with respective apertures of the mask. Static rneans are provided for making the Ithree electron beams converge and pass through the same aperture at the center of the shadow mask plate. rl'he three beams, after passing through the shadow mask, respectively strike three phosphor dots each emitting light of a different color. All three beams are deected by a common horizontal and Vertical deflection system so that the beams systematically scan the kinescope target. The more the three beams are deflected from the center of the target, the greater may be the misconvergence of the beams when they reach the shadow mask. lt is, therefore, customary to provide dynamic electromagnetic means for correcting the misconvergence of the beams as a function of the angular deflection of the beams from the center of the kinescope target. 'For this purpose, `current waveforms of generally parabolic shape are derived from the horizontal and vertical deflection circuits and are employed, in conjunction with three convergence electromagnets, to dynamically converge the three beams so that they pass through the same aperture in the shadow mask at all points of the entire scanned area of the kinescope target.

Careful adjustment of the dynamic convergence circuits is needed so that each convergence electromagnet is energized by a current having such amplitude and wave shape as to effect the desired beam convergence at all points on the kinescope target electrode. ln some prior art arrangements, after beam convergence has been achieved initially in one area of the kinescope screen, the adjustment of the convergence circuit controls in order to achieve convergence in another area of the kinescope screen has been found to so aiiect the initial beam convergence as to cause considerable misco-nvergence of the beams in the first screen area. Consequently, a readjustment to achieve beam convergence in the rst screen area has been necessary and, in most cases, stil-l further repeated readjustments of the controls to achieve beam convergence in some other screen areas has been required.

One of the diiculties in achieving beam convergence with the prior art systems is that such systems were provided with identical controls for all three of the electromagnet windings energized by waves at the vertical deection frequency. Even though beam misconvergence could be detected readily in a picture being reproduced, no corrective adjustments of the prior art controls were immediately feasible. Such convergence adjustments required the use of test apparatus which would display either a dot pattern or a cross-hatch pattern of vertical and horizontal lines on the screen of the ki-nescope.

it is an object of the presen-t invention to provide an improved circuit arrangement by which to more readily effect the convergence of the three electron beams of a tricolor kinescope.

Another object of the present invention is to provide an improved beam convergence system in which two of the three electron beams may be converged simultaeously at vertical deflection frequency by means of controls common to the electromagnet convergence coils of the two electroma-gnets associated with said two electron beams.

Still another object of the invention is to provide an improved and simplified beam convergence system by which satisfactory beam convergence at vertical deflect-ion lfrequency may be achieved by using a regularly reproduced picture as a guide, thereby obviating the use of special test apparatus.

In accordance with this invention the total energizing current for the windings of two of the convergence electromagnets is adjusted in amplitude by one control device and the division of this current between the two windings to effect the desired convergence of two of the electron beams is achieved by a second control device.

In accordance with one practical embodiment of the invention, the amplitude of a substantially parabolic current wave is adjusted by a master amplitude control associated with the series connection of the windings of twoof the convergence electromagnets and the division of the parabolic current wave between the two windings is adjusted by a diderential amplitude control connected in shunt with the ltwo electromagnet windings. Similarly, a master tilt control is employed to adjust the amplitude and polarity of a sawtooth current wave -for impression upon the two electromagnet windings so as to provide the required tilt or phasing of the parabolic current wave to achieve the desired beam convergence. Also, a diftferential tilt control is connected to the windings of the two electroma'gnets in a manner to effect the desired division of the sawtooth current wave between the two electromagnet windings.

The amplitudes of the parabolic and sawtooth current waves impressed upon the third electromagnet winding are separately adjusted by individual controls.

lFor a better understanding of the invention together with additional objects, features and advantages thereof, reference will be made to the accompanying drawings in which:

FGURE l is a schematic circuit diagram or" apparatus for controlling the convergence electromagnets at :the vertical deilection frequency embodying the invention;

FIGURE 2 is a fragmentary sectional View of the neck portion of a color kinescope showing the relationship of the convergence electromagnets and the electron beams controlled thereby;

EGURE 3 is a simplied showing of the ygreen and red beam convergence apparatus of FiGURE l;

FGURES 4a, 4b, 5o, 5b, 6a and 6b are `diagrammatic representations of typical movements of the electron beams which are effected by ythe control circuits of FlG- URE 1 at different stages of the convergence procedure; and,

FIGURE 7 is another diagram illustrative of the operation of the convergence apparatus in accordance with this invention.

Reference first is made to FGURE l of the drawings for a description of `the circuits and apparatus comprising the present invention. lt will be understood that a color television receiver, .in which the present invention is embodied, includes all of the necessary apparatus for receiving a composite color television signal conforming to the present standards established by the 4Federal Communications Commission and for processing such signal for impression upon an ima-ge reproducing device such as a shadow mask color kinescope of the RCA type 21CYP22 or 2lCYP22A.

FlGURE l shows a vertical deflection output tube Ll having in its anode circuit a primary winding 12 of an output transformer 13. One of the secondary windings 14 of this transformer is coupled as indicated in the usual manner to the vertical windings of a deection yoke (not shown) for deiecting the three electron beams of the color kinescope to scan the luminescent screen of the kinescope vertically at the rate of approximately 60 fields per second. It is to be understood that, horizontal windings of the yoke also will be energized to deflect the beams to scan the screen horizontally at the rate of approximately 15,750 lines per second in the usual manner.

The cathode circuit of the vertical output tube 11 in-V cludes a resistor 15 which is bypassedby a capacitor 15, across which cathode circuit there is developed a substantially sawtooth voltage wave 17 at the vertical deflection frequency.

The cathode of the vertical output tube 11 is coupled by means of a series resistor 1S which is shunted by a capacitor 19 to the vertical frequency windings of the green, red and blue convergence electromagnets 2 1, 22 and 23, respectively. By means of the resistor 1S and shunting capacitor 19, the A.C. and D.C. components of the sawtooth voltage wave 17 are so proportioned that the currents which are caused to flow through the vertical frequency windings of the convergence electromagnets 21, 22 and 23 always have substantially the same magnitudes at the time that the electron beams are tracing the horizontal lines of the raster at the center of the screen, irrespective of the particular shapes of the convergence currents and their peak-to-peak amplitudes.

The impression of the sawtooth voltage wave 17 upon the convergence apparatus causes an integration of this wave such that the convergence electromagnet windings 25 and 26 are traversed by a substantially parabolic convergence current wave 24. The amplitude of the parabolic current wave for the green and red convergence electromagnet windings 25 and 26 respectively is controlled by a master amplitude control potentiometer 27.

The vertical windings 25 and 26 of the green and red convergence electromagnets 21 and 22 respectively are connected in series to the movable contact of a master tilt control potentiometer 29, the resistive element of which is connected to the terminals of another secondary winding 31 of the vertical deiection output transformer i3. The center of this winding is grounded to provide a return path for the currents flowing in the windings of the convergence electromagnets. Pulse voltage waves 32 and 33 or" opposite polarity are developed respectively in the coils 31a and 31b of the transformer winding and arc available at the terminals of the winding. The impression of such pulses upon the convergence apparatus causes an integration of the pulses such that the convergence windings 25 and 26 are traversed by a substantially sawtooth current wave 34, the amplitude and polarity of which is determined by the adjustment of the master tilt amplitude control potentiometer 29. The sawtooth current wave 34 is added to the generally parabolic current Wave 24 in the usual manner to tilt or phase (ie, shape) the parabolic Wave to effect the desired beam convergence at substantially all points of the scanned raster.

A diiferential amplitude control potentiometer 35 has its resistive element connected across the series arrangement of the windings 25 and 26 of the green and red convergence electromagnets 21 and 22 respectively. The junction point 36 between the green and red windings 25 and 26 is connected to the center point of still another secondary winding 37 of the vertical deflection output transformer 13. Pulse voltage waves 32a and 33a of opposite polarity are developed respectively in the coils 37a and 37b of this secondary winding and are available at the terminals of the winding. The terminals of this winding are connected to the terminals of the resistive component of a differential tilt control potentiometer 3S. The movable contacts of the two differential potentiometers 35 and 38 are connected together. The adjustment of the movable contact of the differential amplitude control potentiometer 35 varies distribution of the parabolic current wave 24 through the respective windings 25 and 26 of the green and red convergence electromagnets 21 and 22. The adjustment of the movable contact of the differential tilt amplitude control potentiometer 38 determines the distribution between the windings 25 and 26 of the green and red convergence electromagnets 21 and 22 of the sawtooth current wave 34 by controlling the combination with this wave of another sawtooth current wave resulting from the integration of voltage pulses 32a, 33a by the convergence apparatus.

The vertical frequency winding 28 of the blue convergence electromagnet 23 is energized by a substantially parabolic current wave 2da, the amplitude of which is adjusted by a blue amplitude control potentiometer 39. This parabolic wave is tilted or phased (i.e., shaped) by means of a suitable sawtooth component 34a, the amplitude and polarity of which is determined by the adjustment of a blue shape control potentiometer 42, the resistive element of which is connected to the terminals of the deection transformer secondary winding 31.

The green, red and blue convergence electromagnets 21, 22 and 23 also are provided with respective windings 43, 44 and 45 which are energized by suitably shaped waves at the horizontal deiection frequency. The energization of these windings forms no part of the present invention. They may be energized by any suitable means such as that shown in Patent No. 2,903,622, granted September 8, 1959, to I. C. Schopp.

FIGURE 2 shows the physical relationship of the convergence electromagnets and the electron beams controlled respectively thereby. This figure is a transverse sectional view of the neck portion of the color kinescope as it appears when viewed from the screen end of the kinescope. The green, red and blue convergence electromagnets 21, 22 and 23 are mounted externally around the neck 46 of the kinescope. The electromagnet structures include pole pieces 47 located internally of the tube neck and extending inwardly from the ends of the substantially U-shaped cores of the electromagnets. Between the pole pieces of each of the electromagnets there is produced a magnetic field which moves the corresponding electron beam 48 radially in the direction of the arrows. There also may be included as part of the convergence electromagnet structure some means for effecting a static convergence of the electron beams 43. The static convergence means may be permanent magnets associated with each of the convergence electromagnets or may comprise a winding on each of the electromagnets for energization by direct current of the proper amplitude and polarity to effect the desired static convergence of the beams.

In FIGURE 3, the various wave sources are shown symbolically and the circuit diagram is rearranged to illustrate better the manner in which the convergence system in accordance with this invention is designed to operate to effect the green and red beam convergence. The same reference characters are used to designate the corresponding components shown in FIGURE 1.

The convergence system of the invention includes a bridge circuit, one parallel branch of which includes the series arrangement of the green and red electromagnet windings 25 and 26 constituting two adjacent bridge arms and the other parallel branch of which includes the resistive element of the differential amplitude control potentiometer 35 constituting the other two adjacent bridge arms. The components connected between the point 35 and the movable contact of the potentiometer 35 constitute a bridging branch of the circuit. The parabolic and sav/tooth currents flowing in this bridge circuit are derived respectively from sources 15 and 31a-31b connected to opposite ends of the bridge-type circuit and are controlled in amplitude respectively by the master amplitude control potentiometer 27 and the master tilt control potentiometer 29, the latter also controlling the polarity of the sawtooth current.

Consideration first will be given to the operation of the system by the parabolic current. With the movable contact of the differential amplitude control potentiometer 35 set at the midpoint of its resistive element and, with a midpoint adjustment of the differential tilt control potentiometer 3S, the bridge circuit is balanced and no current ows in the bridging branch. Under these conditions the windings 25 and 26 are traversed by substantially equal parabolic currents flowing in the same direction in both windings, as indicated by the polarizing dots. Any adjustment of the master amplitude control potentiometer 27 causes both the green and red electron beams to move radially in the same sense with respect to the longitudinal axis of the kinescope and by the same amount. Assume that the adjustment of the potentiometer 27 increases the parabolic current and that both green and red beams move toward the kinescope axis.

If now the movable contact of the differential amplitude control potentiometer 35 is moved to the right of center as viewed in FIGURE 3, the bridge circuit is unbaianced. Current now ows in the bridging circuit in such sense that the parabolic current in the green electromagnet winding 25 is increased by a certain amount and the parabolic current in the red electromagnet winding 26 is decreased by a like amount. The green beam is moved more toward the kinescope axis and the red beam is moved away from this axis by the same distance. A movement of the movable contact of the differential amplitude control potentiometer 35 to the left of center as viewed in the drawing has the effect of unbalancing the bridge circuit so that current flows in the bridging circuit in the opposite sense, thereby decreasing the parabolic current in the winding 25 and increasing such current in the winding 25 by a like amount. Such adjustment moves the green beam away from the kinescope axis and moves the red beam more toward the axis.

The amplitude and differential control of the sawtooth current 34 derived from the source 31a-31h is effected in a manner similar to that described for the parabolic current. The magnitude and polarity of the total sawtooth current flowing in this bridge circuit is determined by the adjustment of the master tilt control potentiometer 29. The division of the sawtooth current between the windings 25 and 25 is determined by the adjustment of the differential tilt control potentiometer 38 in a manner somewhat similar to that by which the division of the parabolic current 24 is eected by the differential amplitude control potentiometer 35 as previously described.

With respect to the sawtooth current, however, the additional source 37e-37b in the bridging circuit is utilized in conjunction with the differential tilt control potentiometer 3S to unbalance the bridge circuit for the sawtooth current and to control the direction of sawtooth current flow in the bridging circuit and thereby to control the distribution of sawtooth current between the green and red electromagnet windings 25 and 26. Assume that the master tilt control potentiometer 29 is adjusted so as to select a given amplitude of the positive going pulse wave 32, thereby causing a sawtooth current of the polarity of the wave 34 and of a given amplitude to flow in the bridge circuit. With the differential tilt control potentiometer 38 set at the center of its resistive element, substantially equal sawtooth currents of the selected polarity flow through the windings 25 and 26. Assume that the adjustment of the potentiometer 29 increases the sawtooth current in such polarity as to move both green and red beams toward the kinescope axis. It will be noted that the pulse waves 32a and 33a produced by the sources 37a and 37b balance out in the bridging circuit and, thus, contribute no current to the windings 25 and 26. If now the movable contact of the potentiometer 33 is moved toward the right of center as viewed in the drawing, the bridge circuit is unbalanced so that sawtooth current flows in the bridging circuit in such polarity as to decrease the sawtooth current in the green electromagnet winding 25 and to increase such current in the red electromagnet winding 25 by a like amount. Such an adjustment causes the red beam to move more toward the kinescope axis and the green beam to move away from this axis by a like amount. A movement of the movable contact of the differential tilt control potentiometer 38 to the left of center unbalances the bridge circuit so that sawtooth current flows in the bridging circuit in the opposite sense, thereby increasing the sawtooth current in the green electromagnet winding 25 and decreasing such current in the red electromagnet winding 26 by a like amount. Thus, the green beam is moved more toward the kinescope axis and the red beam is moved away from this axis by a like amount.

T he basic principle underlying the dynamic convergence control of the green and red electron beams by means of the apparatus or FIGURE l may be better understood by reference to FIGURES 4a, 4b, 5a, 5b, 6a and 6b. These figures show a typical misconvergence of the green and red electron beams and the convergence of them by apparatus embodying this invention. The rectangles designated G and R in these figures respectively represent green and red colored light spots on the luminescent screen of the color kinescope. It is assumed for the following de scription that the usual adjustments of the various beam positioning elements will have been made so as to assure color purity and static convergence of the three beams at the center of the raster on the luminescent screen of the kinescope. By color purity is meant the control of the electron beams such that one beam strikes only green phosphor areas of the luminescent screen, another of the beams strikes only red screen areas and the third beam strikes only blue screen areas. Adjusting the beams for color purity, however, does not necessarily achieve convergence of the three beams in all areas of the screen.

From an inspection of FIGURE 2 it may be seen that, if

the green and red beams can first be made to converge with one another at any given point on the luminescent screen, the blue beam may be made to converge with the red and green beams by moving the blue beam vertically and/or horizontally.

@ne of the features of the present invention is the sim.- plitcation of the convergence of the red and green beams so that the blue beam subsequently may also be brought into convergence therewith at all points on the luminescent screen with a minimum of interaction between the various adjustments of the beam convergence apparatus. In Athis way, having achieved convergence of the beams in one area or" the screen, other adjustments may be marde to achieve convergence in other areas of the screen, without affecting to any appreciable degree, t-he convergence achieved in the first screen area.

In making the convergence adjustments, a color bar generator such as the lRCA VVR-61A may be used to display a cross-hatch of spaced vertical and horizontal bars on the luminescent screen or" the kinescope. Each bar of such `a pattern consists of green, red and blue lines. When the three beams are properly converged in all areas of the screen, all bars of the pattern are white. When the beams are not properly converged, t-he colored lines of the bars are discernible as indicated in FIGURE 7. This FIGURE 7 illustrates only those portions of such `a bar pattern as are necessary for achieving the desired beam convergence at vertical deflection frequency. The significant bars are a single, centrally located vertical bar and the upper and lower horizont-al lbars of the complete bar pattern. Also, in effecting the initial convergence of the green and red beams, it frequently is advantageous to blank out the blue electron beam such as by shuntin'g the control grid of the blue beam electron gun to ground through a resistor of the order of 100,000l ohms. It is to be noted that, in the lower part of FIGURE 7, the green, -blue and red horizontal lines Gh, Bh and Rh are mutually spaced from one another and also that the vertically extending green, red and blue lines Gv, Bv and Rv also are mutually spaced at their intersections with the lower group of lines. A similar condition exists in the upper part of this gure. This .indicates that at least the green and red beams are misconverged since there should be no spacing between either horizontal orvertical lines. The two points G and R at which the green and red vertical lines intersect respectively with the green and red horizontal lines should coincide when the beams are properly converged.

It is rto be understood that each line consists of a plurality of elemental areas. Assume that the rect-angular arcas G1 and R1 of FIGURES 4a, 4b, 5a, 5b, 6a and 6b are the elemental areas (greatly enlarged) at the two intersecting points G and R of the horizontal and vertical green and red lines in the lower part of FIGURE 7. FIGURE 4a represents the relative positions of the green and red areas G1 and R1 typically misconverged as in FIGURE 7. Also, FIGURE 4b illustrates the fragmentary portion of the color bar pattern shown in FIGURE 7, neglecting the blue beam which is assumed to be cut-ofic as previously described. rFhe arrows shown in FIGURE 4a, indicate the paths along which the green and red areas G1 and R1 may be 'caused to move by changing the energization of the green and red convergence electro-magnets 21 and 22 as shown in FIGURE 2.. It is evident from FIGURE 4a that the green and red areas Gl and RI maybe made to coincide only at the point O which is the intersection of the two paths of movement for the beam-s as controlled by the convergence electromagnets. FIG- URE 4b indicates that the areas Gl and Ri are spaced in the bar pattern both vertically and horizonrtaliy from one another.

With reference to FIGURE l, the master amplitude control potentiometer 27 is adjusted to vary the parabolic current energization of the green and red electromagnet windings .25 and 26 in the same magnitude and in the same sense. This causes the electron beams to move radially so that the green area G1 of FIGURE 4a moves downwardly and to the right toward the intersecting point O to the position indicated by the rectangle GZ in FIG- URE a. At the same time, the described manipulation of the master amplitude control potentiometer 27 causes the red area R1 to move downwardly and toward the left through the intersecting point O to the position indicated by the rectangle R2 in FIGURE 5a. By reason of the fact `that the manipulation of the potentiometer 2.7 causes substantially equal changes in fthe parabolic current ilofw'ing through the green and red convergence electromagnet windings 25 and 26 respectively, it is seen from FIGURE 5a that the green area travels substantially the same distance between the points G1 and GZ as the distance traveled by the red area yfrom position Rl to position R2. In the G2 and R2 positions shown in FIGURE 5a; it is to be noted the green and red areas are in the same vertical line but are in different horizontal lines. This positioning also is illustrated with reference to the color bar pattern in FIGURE 5 b. The spacing between the horizont-al lines Gh `and Rh is substantially the same as it is in FIGURE 4b. The ventical lines Gv and Rv, however, have been moved toward one another so that they are vertically superimposed as indicated in FIGURE 5b. The vertical line GvRv in this gure is `approximately midway between the positions of the vertical red and green lines Gv and Rv of AFIGURE 4b.

Again with reference to FIGURE l, the differential amplitude control potentiometer 35 is adjusted so as Lo cause parabolic current changes in the green and red electromagnet windings Z5 and 26 of the same magnitude but of opposite senses. In the present illus-tration, the sense of the current change in the red electromagnet Winding 26gis opposite -to that produced by the previously described adjustment of the master amplitude control potentiorneter 27. The sense of the current change in the green electromagnet winding 25, howeven'is the same as that produced by manipulation of the potentiometer 27. The effect of such a manipulation of the diierential amplitude control potentiometer 35 is to move the red area R2 back to the intersecting point O as shown in FIGURE 6.1. Similarly, the effect of changing the current in the green electromagnet winding 2S as described is to move the green area G2 farther along its line of movement to the intersecting point O. It is seen that now the red and green areas are converged. As indicated in the bar pattern on the screen in FIGURE 6b, the `green and 4red horizontal lines Gh and Rh now also are superimposed respectively on one another.

Reviewing the manipulation of the master amplitude control potentiometer 27 `and the differential amplitude potentiometer 35 with reference to the more complete har pattern of FIGURE 7, the adjustment of these controis is made while observing the illustrated signicant lines of the bar pattern. Manipulation of the master arnplitude control potentiometer 27 superimposes the centrally located green and red vertical lines in the lower portion of the bar pattern. The subsequent manipulation of the differential amplitude control potentiometer 3S causes the `lower set of green and red horizontal lines to be superimposed.

The master tilt control potentiometer 29 and the differential tilt control potentiometer 38 of FIGURE l affect the beam convergence at vertical deection frequency in the upper portion of the bar pattern of FIGURE 7 in a manner similar to that described with reference to the convergence control in the lower portion of the bar pattern by potentiometers 27 and 35 of FIGURE l. Manipulation of the master tilt control potentiometer 29 causes a change in the total sawtooth current flowing in windings 25 and 26 of the green and red convergence electromagnets 2l and 22. This current change is in the same magnitude and in the same Sense in both electromagnet windings. Accordingly, the green and red elemental areas making up the lines of the bar pattern in the upper portion ofVFIGURE 7 are moved from positions such as those indicated in FIGURE 4a to positions such as indicated in FIGURE 5a so that the green and red areas are in vertical alignment. Manipulation of the differential tilt control potentiometer 3S changes the sawtooth currents in the electromagnet windings 25 and 26 in the same magnitude but in opposite senses. This causes the elemental red and green areas on the luminescent screen to move from positions such as indicated in FIGURE 5a to a position such as indicated in FIGURE 6a wherein the red and green areas are superimposed.

Again with particular reference to FIGURE 7, manipulation of the master tilt control potentiometer 29 of FIG- URE l superimposes the centrally located green and red vertical lines in the upper portion of the bar pattern. The subsequent manipulation of the diilerential tilt control potentiometer 38 of FIGURE 1 causes the superposition of the red and green horizontal lines in the upper portion of the bar pattern.

When the described convergence of the red and green electron beams at vertical deflection frequency has been achieved in accordance with the foregoing description, the blue electron beam may be turned on, if during the adjustment of the red and green convergence control potentiometers 27, 29, 35 and 3S it had been blanked out. Any misregistration of the vertical and horizontal blue lines of the bar pattern with respect to the green and red lines is achieved by suitable manipulation of the blue amplitude control potentiometer 39 and the blue shape control potentiometer 4Z. Such blue beam convergence apparatus and itsioperation is known and, hence, needs no further description in order to understand the present invention.

While the present invention does not completely eliminate interaction between the various controls in effecting dynamic beam convergence at the vertical deflection frequency, it reduces such interaction substantially so as to require very little, if any, repetition of the series of adjustments. It is seen from FEGURE 3 that, by reason of the interrelation of the circuits and control potentiometers for the parabolic and sawtooth currents, some such interaction may be expected. In general, the amplitude control potentiometers 27 and 29 converge vertical lines of the picture and the differential control potentiometers 35 and 38 control the convergence of horizontal picture lines. As indicated from the foregoing description, the potentiometers 27 and 35 controlling the parabolic current have a greater effect upon beam convergence in the lower part of the picture than in the upper part of the picture. Conversely, the potentiometers 29 and 38 controlling the sawtooth current have a greater eiect at the top part of the picture than at the bottom. Consequently, some readjustment of a previously adjusted control sometimes may be necessary after an adjustment of another control in order to achieve good dynamic beam convergence over the entire picture area as a final result.

rThe foregoing description of the functions of the various convergence controls and the manner in which they operate to effect the desired dynamic convergence of the green and red electron beams at the vertical deilection frequency is not necessarily the most practical order of making these adjustments. The following sequence of operations is one which is presently preferred for use in practice of apparatus embodying this invention after rst having achieved static convergence of the red, green and blue beams at the center of the kinescope screen by suitable adjustment of the static convergence means such as the permanent magnets previously referred to:

(l) rl`he master amplitude control potentiometer 27 is adjusted to superimpose the green and red vertical lines at the bottom of the center bar.

(2) The master tilt control potentiometer Z is adjusted to superimpose the green and red vertical lines at the top of the center bar.

(3) Alternate steps l and 2, ir" necessary, to achieve equal convergence of the green and red vertical lines from top to bottom.

(4) The differential amplitude control potentiometer 35 is adjusted to superimpose the green and red horizontal lines at the bottom center of the screen.

(5) The differential tilt control potentiometer 3S is adjusted to superimpose the green and red horizontal lines at the top center of the screen.

(6) Alternate steps 4 and 5, if necessary, to achieve equal convergence of all green and red horizontal lines from top to bottom.

As previously indicated, registration of the blue lines of the bar pattern at vertical deiiection frequency is achieved by proper manipulation of the blue amplitude control potentiometer 39 and the blue shape control potentiometer 42.

After having achieved the desired beam convergence at the vertical deflection frequency as previously described in accordance with the present invention, beam convergence at the horizontal deection frequency should be effected in accordance with whatever prior art apparatus is used for this purpose. Since such apparatus is not part of the present invention, no disclosure or description thereof is needed to understand this invention and hence such disclosure has not been included.

rThis invention has a number of advantages over vertical dellection frequency convergence control circuits previously used in commercial color television receivers. The vertical output transformer 13 of FIGURE l requires one more secondary than used in prior art arrangements such as that disclosed in Schopp Patent No. 2,993,- 622. The additional cost of such a winding, however, is more than oifset by the reduced cost of the windings 25 and 26 of the green and red convergence electromagnets, thereby resulting in a net cost reduction. In previously used arrangements where the vertical convergence windings 25 and 26 are operated in parallel as in the Schopp patent, a relatively large number of turns has been required in order to obtain a sufficiently high Q to perform the integration of the wave energy derived from the cathode circuit of the vertical output tube lll to produce a substantially parabolic current wave in the convergence electromagnet windings. A smaller number of turns is required in each of the windings 25' and 26 to achieve the necessary integration by virtue of the series connection of these two windings. Consequently, the cost of the present windings is less than that of the previously used windings by such an amount as to produce the described net cost reduction.

Also, the vertical convergence control circuit in accordance with the present invention enables the achievement of vertical convergence of the three electron beams `of a color kinescope with such increased facility that in many cases satisfactory convergence can be effected while the receiver is being operated to produce a picture, thereby obviating the use of any special test apparatus such as a color bar generator as previously described. Most television pictures include lines which are suiciently vertical and horizontal in the desired places referred to in the aforegoing description. Suitable adjustment of the various control potentiometers shown in FIGURE l may be made generally in accordance with the foregoing description merely by using the somewhat horizontal and vertical lines of the picture. Preferably, such a picture should be reproduced in black and white. If a picture is being reproduced from a received color television signal, it may be reproduced in black and white merely by sui-tably operating the color controls provided in the receiver to temporarily disable the color circuits.

What is claimed is:

l. Convergence apparatus for a tricolor kinescope in which three electron beams traverse pre-deflection paths that are spaced respectively about the longitudinal axis of the kinescope and are angularly deflected both horizontally and vertically to scan a common rectangular raster at a target electrode structure including a luminescent screen having phosphors capable `of producing three diiferent colors of light when excited by said respective electron beams, said apparatus comprising in combination: three electromagnets respectively mounted adjacent to said predeflection beam paths and having windings energizable to produce respective elds transverse to said beam paths and in directions to move said respective electron beams radially relative to said longitudinal kinescope axis; means connecting two of said electromagnet windings together for simultaneous control; a first source of periodic energy at the vertical deilection frequency and of a character to cause energizing current of one particular waveform to traverse said two windings when said iirst energy source is connected -to said two windings; means including a rst master amplitude controlling potentiometer for connecting said rst energy source to a series arrangement of said two windings and for varying the current of said one particular waveform in said two windings in the same sense and in the same magnitude; means including a rst dilerential amplitude controlling potentiometer connected to said two windings in a manner to vary the current of said one particular waveform in said two windings in opposite senses and in the same magnitude; a second source of periodic energy at the vertical deflection frequency and of a character to cause energizing current of a second particular waveform to traverse said two windings when said source is connected to said two windings; means including a second master amplitude controlling potentiometer for connecting said second energy source to said series arrangement of said two windings and for varying the current of said second particular waveform in said two windings in the same sense and in the same magnitude; and means including a second differential amplitude controlling potentiometer connected to said two windings in a manner to vary the current 0f said i i second particular waveform in said two windings in opposite senses and in the same magnitude.

2. Convergence apparatus for a tricolor kinescope in which three electron beams traverse pre-deiiection paths -that are spaced respectively about the longitudinal axis of the kinescope and are angularly deliected both horizontally and vertically to scan a common rectangular raster at a target electrode structure including a luminescent screen having phosphors capable of producing three ditferent colors of light when excited by said respective electron beams, said apparatus comprising in combination: three electromagnets respectively mounted adjacent t said pre-deiiection beam paths and having windings energizable to produce respective ields transverse to said beam paths and in directions to move said respective electron beams radially relative to said `longitudinal kinescope axis; means connecting two of said electromagnet windings together for simultaneous control; a iirst source of periodic energy at the vertical deection frequency and of a character to cause energizing current of a parabolic waveform to traverse said two windings when said first energy source is connected to said two windings; means including a master amplitude controlling potentiometer for connecting said first energy source to a series arrangement of said two windings and for varying the current of said parabolic waveform in said two windings in the same sense and in the same magnitude; means including a diierential amplitude controlling potentiometer connected to said two windings -in a manner to vary the current of said parabolic waveform in said two windings in opposite senses and in the same magnitude; a second source of periodic energy at the vertical deection frequency and of a character to cause energizing current of a sawtooth waveform to traverse said two windings when said source is connected to said two windings; means including a master tilt controlling potentiometer for connecting said second energy source to a said series arrangement of said two windings and for varying the current of said sawtooth waveform in said two windings in the same sense and in the same magnitude; and means including a differential tilt controlling potentiometer connected to said two windings in a manner to vary the current of said sawtooth waveform in said two windings in opposite senses and in the same magnitude.

3. In a cathode ray tube image reproducing system wherein a plurality of electron beam components which traverse pre-deflection paths spaced respectively about the longitudinal axis of the tube are angularly defiected by horizontal and vertical beam deflection apparatus to scan a raster at a target electrode, apparatus for simultaneously converging two of said beams comprising: two electromagnets respectively mounted adjacent to said pre-deflection paths of said two beams and having windings energizable to produce respective fields of a character to move said two beams radially relative to said longitudinal axis; means connecting the windings of said two electromagnets as two adjacent arms of a bridge circuit; potentiometer means having a resistive element connected as the other two adjacent arms of said bridge circuit in parallel with said two windings so that the junction points betweensaid windings and the resistive element of said potentiometer means form input terminals of said bridge circuit; means connecting the movable contact of said potentiometer means to the junction point between said two electromagnet windings to form a bridging circuit; a 4iirst source of energy connected to the terminals of said bridge circuit to cause a iirst current flow in the arms of said bridge circuit; means including the contact of said potentiometer means to vary the magnitude and sense of said tirst current flow in said bridging circuit, thereby to apportion said first current ow between said t-wo electromagnet windings; a second source of energy connected to the terminals of said bridge circuit to cause a second current flow in the arms of said bridge circuit; a third source of energy and a second potentiometer u,lisses means connected in said bridging circuit, the resistive element of said second potentiometer means being connected across said third energy source and the contact of said second potentiometer means being connected to the Contact of said iirst potentiometer means; and means including the movable contact of said second potentiometer means to vary the magnitude and sense of said second current ilow in said bridging circuit, thereby to apportion said second current ilow between said two electromagnet windings.

4. ln a cathode ray tube image reproducing system wherein a plurality of electron beam components which traverse pre-deiiection paths spaced respectively about the longitudinal axis of the tube are angularly deliected by horizontal and vertical beam deection apparatus to scan a raster at a target electrode, apparatus for simultaneously converginT two of said beams comprising: two electrcmagnets respectively mounted adjacent to said predeiiection paths of said two beams and having windings energizable to produce respective elds of a character to move said two beams radially relative to said longitudinal axis; means connecting the windings of said two electromagnets as two adjacent arms of a bridge circuit; potentiometer means having a resistive element connected as the other two adjacent arms of said bridge circuit in parallel with said two windings so that the junction points between said windings and the resistive element of said potentiometer means `form input terminals of said bridge circuit; means connecting the movable contact of said potentiometer means to the junction point between said two electromagnet windings to form a bridging circuit; a first source of energy connected to the terminals of said bridge circuit, said iirst source of energy being of a character to cause a current of substantially parabolic wave- `form to flow in the arms of said bridge circuit; means including the contact of said potentiometer means to vary the magnitude and sense of current i'low in said bridging circuit, thereby to apportion said parabolic current flow between said two electromagnet fwindings; a second source of energy connected to the terminals of said bridge circuit, said second source of energy being of a character to cause a current of substantially sawtooth waveform to iiow in the arms of said bridge circuit; a third source of energy and a second potentiometer means connected in said bridging circuit, said third source of energy being of a character to cause a current of substantially saw tooth waveform to flow in the arms of said bridge circuit and in said bridging circuit, the resistive element of said second potentiometer means being connected across said third energy source and the contact of said second potentiometer means being connected to the contact of said iirst potentiometer means; and means including the movable Contact of said second potentiometer means to vary the magnitude and sense of said sawtooth current flow in said bridging circuit, thereby to apportion said sawtooth current new between said two electromagnet windings.

5. In a cathode ray tube image reproducing system wherein a plurality of electron beam components which traverse pre-deflection paths spaced respectively about the longitudinal axis of the tube are angularly deflected by horizontal and vertical beam deflection apparatus to scan a raster at a target electrode, apparatus for simultaneously converging two of said beams comprising: electromagnets respectively mounted adjacent to said predetermined beam paths and having windings energizable to roduce respectivev fields of a character to move said respective beams radially relative to said longitudinal axis; means connecting the windings of said two electromagnets as two adjacent arms of a bridge circuit; impedance means connected as the other two adjacent arms of said bridge circuit in parallel with said two windings so that the junction points between said windings and said impedance means form input terminals of said bridge circuit; a bridging circuit connecting a point on said im- 13 pedance means to the junction point between said two electromagnet windings; a rst source of opposite polarity energy of a character when connected to the terminals of said bridge circuit to cause an energizing current ow in the arms of Said bridge circuit; first potentiometer means having a resistive element connected to said first source of energy and a movable contact connected to one of said bridge circuit terminals; means including the contact of said trst potentiometer means to vary the magnitude and polartiy of the energy supplied to said bridge circuit; a second source of opposite polarity energy and a second potentiometer means connected in said bridging circuit, said second source of energy being of a character similar to said rst source of energy, the resistive element of said second potentiometer means being connected across said second energy source, and the contact of said second potentiometer means being connected to said point on said impedance means; and

References Cited in the tile of this patent UNITED STATES PATENTS 2,677,779 Goodrich s May 4, 1954 2,880,360 4Hauge Mar. 3l, 1959 2,880,364 Kolesnik et al. Mar. 31, 1959 2,987,647 Armstrong `June 6, 1961 OTHER REFERENCES Color Television Service Data, 1960, No. T5, for CTClO Chassis Series, RCA Victor, pp. 32-33, May 10, 1960. 

1. CONVERGENCE APPARATUS FOR A TRICOLOR KINESCOPE IN WHICH THREE ELECTRON BEAMS TRANSVERSE PRE-DEFLECTION PATHS THAT ARE SPACED RESPECTIVELY ABOUT THE LONGITUDINAL AXIS OF THE KINESCOPE AND ARE ANGULARLY DEFLECTED BOTH HORIZONTALLY AND VERTICALLY TO SCAN A COMMON RECTANGULAR RASTER AT A TARGET ELECTRODE STRUCTURE INCLUDING A LUMINESCENT SCREEN HAVING PHOSPHORS CAPABLE OF PRODUCING THREE DIFFERENT COLORS OF LIGHT WHEN EXCITED BY SAID RESPECTIVE ELECTRON BEAMS, SAID APPARATUS COMPRISING IN COMBINATION: THREE ELECTROMAGNETS RESPECTIVELY MOUNTED ADJACENT TO SAID PREDEFLECTION BEAM PATHS AND HAVING WINDINGS ENERGIZABLE TO PRODUCE RESPECTIVE FIELDS TRANSVERSE TO SAID BEAM PATHS AND IN DIRECTIONS TO MOVE SAID RESPECTIVE ELECTRON BEAMS RADIALLY RELATIVE TO SAID LONGITUDINAL KINESCOPE AXIS; MEANS CONNECTING TWO OF SAID ELECTROMAGNET WINDINGS TOGETHER FOR SIMULTANEOUS CONTROL; A FIRST SOURCE OF PERIODIC ENERGY AT THE VERTICAL DEFLECTION FREQUENCY AND OF A CHARACTER TO CAUSE ENERGIZING CURRENT OF ONE PARTICULAR WAVEFORM TO TRANSVERSE SAID TWO WINDINGS WHEN SAID FIRST ENERGY SOURCE IS CONNECTED TO SAID TWO WINDINGS; MEANS INCLUDING A FIRST MASTER AMPLITUDE CONTROLLING POTENTIOMETER FOR CONNECTING SAID FIRST ENERGY SOURCE TO A SERIES ARRANGEMENT OF SAID TWO WINDINGS AND FOR VARYING THE CURRENT OF SAID ONE PARTICULAR WAVEFORM IN SAID TWO WINDINGS IN THE SAME SENSE AND IN THE SAME MAGNITUDE; MEANS INCLUDING A FIRST 